It is known that a liquid crystal optical device is able to vary its refractive index distribution to vary with application of voltages by using the birefringent properties of liquid crystal molecules. There is also a stereoscopic image display device that includes such a liquid crystal optical device and an image display unit.
In such a stereoscopic image display device, the refractive index distribution of the liquid crystal optical device is varied to switch the stereoscopic image display device between a state in which an image displayed on the image display unit is caused to be incident on the eyes of a viewer as is displayed and a state in which an image displayed on the image display unit is caused to be incident on the eyes of the viewer as multiple parallax images. With this arrangement, a high-definition two-dimensional image display operation and a three-dimensional image display operation are realized, where the three-dimensional image display operation includes an autostereoscopic viewing for the naked eyes with the multiple parallax images. The liquid crystal optical device used in the stereoscopic image display device is expected to have a suitable optical properties for comfortable viewing.